Phase modulation is a method of modulating wireless data signals to represent information as variations in the instantaneous phase of a carrier wave. Conventionally, phase modulation has not been widely used since it requires more complex receiving hardware and since ambiguity problems have often arisen when determining whether, for example, the signal has changed phase by +180° or −180°. Instead, existing wireless communication systems often employ amplitude-shift keying (ASK), which is another modulation method that represents digital data as variations in the amplitude of a carrier wave. Generally, the maximum communication speed in these systems is approximately 848 kilobits per second and is typically done at ASK having 10% modulation index.
Currently, there are several investigations to improve communication speed using phase modulation with more than one bit of information coding. However, due to bandwidth limitations in existing systems, it is not possible to increase the frequency of 848 kilohertz, which is approximately 1.2 microseconds per bit. As such, investigations involving phase modulation have attempted to modulate more than one bit of information during a given period. Certain techniques such as phase jitter modulation have attempted to utilize the advantages provided by phase modulation. However, conventional methods do not detect multiple phase angles and require a period of downtime for the detection circuit to recalibrate before being ready to receive further data on the phase-modulated signal.